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Merged ECP memory usage optimizations

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This commit is contained in:
Paul Bakker 2013-12-31 10:32:50 +01:00
parent 53e1513fea 26bc1c0f5d
commit c73879139e
5 changed files with 59 additions and 28 deletions
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1
ChangeLog
View file

@ -19,6 +19,7 @@ Changes
* More constant-time checks in the RSA module
* Split off curves from ecp.c into ecp_curves.c
* Curves are now stored fully in ROM
* Memory usage optimizations in ECP module
Bugfix
* Fixed bug in mpi_set_bit() on platforms where t_uint is wider than int

1
include/polarssl/config.h
View file

@ -1890,6 +1890,7 @@
//
#define POLARSSL_ECP_MAX_BITS 521 /**< Maximum bit size of groups */
#define POLARSSL_ECP_WINDOW_SIZE 6 /**< Maximum window size used */
#define POLARSSL_ECP_FIXED_POINT_OPTIM 1 /**< Enable fixed-point speed-up */
// Entropy options
//

26
include/polarssl/ecp.h
View file

@ -178,11 +178,33 @@ ecp_keypair;
* Minimum value: 2. Maximum value: 7.
*
* Result is an array of at most ( 1 << ( POLARSSL_ECP_WINDOW_SIZE - 1 ) )
* points used for point multiplication.
* points used for point multiplication. This value is directly tied to EC
* peak memory usage, so decreasing it by one should roughly cut memory usage
* by two (if large curves are in use).
*
* Reduction in size may reduce speed for big curves.
* Reduction in size may reduce speed, but larger curves are impacted first.
* Sample performances (in ECDHE handshakes/s, with FIXED_POINT_OPTIM = 1):
* w-size: 6 5 4 3 2
* 521 145 141 135 120 97
* 384 214 209 198 177 146
* 256 320 320 303 262 226
* 224 475 475 453 398 342
* 192 640 640 633 587 476
*/
#define POLARSSL_ECP_WINDOW_SIZE 6 /**< Maximum window size used */
/*
* Trade memory for speed on fixed-point multiplication.
*
* This speeds up repeated multiplication of the generator (that is, the
* multiplication in ECDSA signatures, and half of the multiplications in
* ECDSA verification and ECDHE) by a factor roughly 3 to 4.
*
* The cost is increasing EC peak memory usage by a factor roughly 2.
*
* Change this value to 0 to reduce peak memory usage.
*/
#define POLARSSL_ECP_FIXED_POINT_OPTIM 1 /**< Enable fixed-point speed-up */
#endif
/*

49
library/ecp.c
View file

@ -791,7 +791,16 @@ static int ecp_normalize_jac_many( const ecp_group *grp,
MPI_CHK( mpi_mul_mpi( &T[i]->X, &T[i]->X, &ZZi ) ); MOD_MUL( T[i]->X );
MPI_CHK( mpi_mul_mpi( &T[i]->Y, &T[i]->Y, &ZZi ) ); MOD_MUL( T[i]->Y );
MPI_CHK( mpi_mul_mpi( &T[i]->Y, &T[i]->Y, &Zi ) ); MOD_MUL( T[i]->Y );
MPI_CHK( mpi_lset( &T[i]->Z, 1 ) );
/*
* Post-precessing: reclaim some memory by shrinking coordinates
* - not storing Z (always 1)
* - shrinking other coordinates, but still keeping the same number of
* limbs as P, as otherwise it will too likely be regrown too fast.
*/
MPI_CHK( mpi_shrink( &T[i]->X, grp->P.n ) );
MPI_CHK( mpi_shrink( &T[i]->Y, grp->P.n ) );
mpi_free( &T[i]->Z );
if( i == 0 )
break;
@ -915,6 +924,8 @@ cleanup:
* due to the choice of precomputed points in the modified comb method.
* So branches for these cases do not leak secret information.
*
* We accept Q->Z being unset (saving memory in tables) as meaning 1.
*
* Cost: 1A := 8M + 3S
*/
static int ecp_add_mixed( const ecp_group *grp, ecp_point *R,
@ -933,13 +944,13 @@ static int ecp_add_mixed( const ecp_group *grp, ecp_point *R,
if( mpi_cmp_int( &P->Z, 0 ) == 0 )
return( ecp_copy( R, Q ) );
if( mpi_cmp_int( &Q->Z, 0 ) == 0 )
if( Q->Z.p != NULL && mpi_cmp_int( &Q->Z, 0 ) == 0 )
return( ecp_copy( R, P ) );
/*
* Make sure Q coordinates are normalized
*/
if( mpi_cmp_int( &Q->Z, 1 ) != 0 )
if( Q->Z.p != NULL && mpi_cmp_int( &Q->Z, 1 ) != 0 )
return( POLARSSL_ERR_ECP_BAD_INPUT_DATA );
mpi_init( &T1 ); mpi_init( &T2 ); mpi_init( &T3 ); mpi_init( &T4 );
@ -1025,7 +1036,7 @@ int ecp_sub( const ecp_group *grp, ecp_point *R,
return( POLARSSL_ERR_ECP_FEATURE_UNAVAILABLE );
/* mQ = - Q */
ecp_copy( &mQ, Q );
MPI_CHK( ecp_copy( &mQ, Q ) );
if( mpi_cmp_int( &mQ.Y, 0 ) != 0 )
MPI_CHK( mpi_sub_mpi( &mQ.Y, &grp->P, &mQ.Y ) );
@ -1184,7 +1195,7 @@ static int ecp_precompute_comb( const ecp_group *grp,
TT[k++] = cur;
}
ecp_normalize_jac_many( grp, TT, k );
MPI_CHK( ecp_normalize_jac_many( grp, TT, k ) );
/*
* Compute the remaining ones using the minimal number of additions
@ -1196,25 +1207,12 @@ static int ecp_precompute_comb( const ecp_group *grp,
j = i;
while( j-- )
{
ecp_add_mixed( grp, &T[i + j], &T[j], &T[i] );
MPI_CHK( ecp_add_mixed( grp, &T[i + j], &T[j], &T[i] ) );
TT[k++] = &T[i + j];
}
}
ecp_normalize_jac_many( grp, TT, k );
/*
* Post-precessing: reclaim some memory by
* - not storing Z (always 1)
* - shrinking other coordinates
* Keep the same number of limbs as P to avoid re-growing on next use.
*/
for( i = 0; i < ( 1U << (w-1) ); i++ )
{
mpi_free( &T[i].Z );
mpi_shrink( &T[i].X, grp->P.n );
mpi_shrink( &T[i].Y, grp->P.n );
}
MPI_CHK( ecp_normalize_jac_many( grp, TT, k ) );
cleanup:
return( ret );
@ -1240,9 +1238,6 @@ static int ecp_select_comb( const ecp_group *grp, ecp_point *R,
MPI_CHK( mpi_safe_cond_assign( &R->Y, &T[j].Y, j == ii ) );
}
/* The Z coordinate is always 1 */
MPI_CHK( mpi_lset( &R->Z, 1 ) );
/* Safely invert result if i is "negative" */
MPI_CHK( ecp_safe_invert_jac( grp, R, i >> 7 ) );
@ -1271,6 +1266,7 @@ static int ecp_mul_comb_core( const ecp_group *grp, ecp_point *R,
/* Start with a non-zero point and randomize its coordinates */
i = d;
MPI_CHK( ecp_select_comb( grp, R, T, t_len, x[i] ) );
MPI_CHK( mpi_lset( &R->Z, 1 ) );
if( f_rng != 0 )
MPI_CHK( ecp_randomize_jac( grp, R, f_rng, p_rng ) );
@ -1319,12 +1315,17 @@ static int ecp_mul_comb( ecp_group *grp, ecp_point *R,
/*
* If P == G, pre-compute a bit more, since this may be re-used later.
* Just adding one ups the cost of the first mul by at most 3%.
* Just adding one avoids upping the cost of the first mul too much,
* and the memory cost too.
*/
#if POLARSSL_ECP_FIXED_POINT_OPTIM == 1
p_eq_g = ( mpi_cmp_mpi( &P->Y, &grp->G.Y ) == 0 &&
mpi_cmp_mpi( &P->X, &grp->G.X ) == 0 );
if( p_eq_g )
w++;
#else
p_eq_g = 0;
#endif
/*
* Make sure w is within bounds.

10
library/memory_buffer_alloc.c
View file

@ -77,6 +77,7 @@ typedef struct
size_t total_used;
size_t maximum_used;
size_t header_count;
size_t maximum_header_count;
#endif
#if defined(POLARSSL_THREADING_C)
threading_mutex_t mutex;
@ -335,6 +336,8 @@ static void *buffer_alloc_malloc( size_t len )
#if defined(POLARSSL_MEMORY_DEBUG)
heap.header_count++;
if( heap.header_count > heap.maximum_header_count )
heap.maximum_header_count = heap.header_count;
heap.total_used += cur->size;
if( heap.total_used > heap.maximum_used)
heap.maximum_used = heap.total_used;
@ -484,8 +487,11 @@ int memory_buffer_alloc_verify()
void memory_buffer_alloc_status()
{
fprintf( stderr,
"Current use: %u blocks / %u bytes, max: %u bytes, malloc / free: %u / %u\n",
heap.header_count, heap.total_used, heap.maximum_used,
"Current use: %u blocks / %u bytes, max: %u blocks / %u bytes (total %u bytes), malloc / free: %u / %u\n",
heap.header_count, heap.total_used,
heap.maximum_header_count, heap.maximum_used,
heap.maximum_header_count * sizeof( memory_header )
+ heap.maximum_used,
heap.malloc_count, heap.free_count );
if( heap.first->next == NULL )